集合表达式运算

文件input.txt，集合表达式((A+B)*C-B)*A
文件input.txt的内容如下：
A = {5, 9, 10, 13, 56 }
B = {15, 8, 20 }
C = {78, 19, 10, 65 }
计算((A+B)*C-B)*A
输出结果：((A+B)*C-B)*A = {10}
+”，“*”，“-”分别表示集合并、交、差运算。

package math;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {//((A+B)*C-B)*A
public static void main(String args[]){

    try {
        while(true){
            BufferedReader br=new BufferedReader(
                    new InputStreamReader(System.in));
            System.out.println("Enter 'exit' withdraw from this program.");
            System.out.print("Enter Expressions >");
            String exp=br.readLine().replace(" ","");
            if(!exp.equals("exit")){
                new MathCollection(exp);
                System.out.println();

            } else { 
                System.exit(0);
            }
        }
    } catch (Exception e) {
        System.out.println("invalid expressions");
    } 


}

}

package math;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

/*

• 离散数学，集合运算，读取三个集合 实现并、交、差运算
• @author david
  

• */
  public class MathCollection {
  private static int[] type;
  private static int[] A,B,C;
  public MathCollection(){}
  public MathCollection(String exp) throws Exception {
  System.out.println("init ollection.");
  initArray();
  operation(exp);
  System.out.print(exp+" = { ");
  for(int a:type){

      System.out.print(a+" ");
  }
  System.out.print("}");
  

  }
  public static String operation(String s) throws Exception{
  if(s.equals("T")){
  return null;
  } else {
  if(ifchar(s)){
  String str=priority(s);
  String a=str.replace("(","").replace(")","");
  System.out.println(" "+s);
  operate(a);
  String strnew=strReplace(s,str,"T");
  return operation(strnew);
  } else {
  return operate(s);
  }
  }
  }
  public static String priority(String s){
  int l,r;
  l = s.lastIndexOf("(");
  String newStr;
  r = s.substring(l).indexOf(")")+1+s.substring(0, l).length();
  newStr = s.substring(l, r);
  return newStr;
  }
  public static boolean ifchar(String s){
  char[] f=s.toCharArray();
  for(char ff:f){
  if(ff=='(') return true;
  }
  return false;
  }

  public static String operate(String exp){
  if(exp.equals("T")){
  return null;
  } else {
  String s1=exp.substring(0,3);
  String a1=s1.substring(0,1);
  String a2=s1.substring(2,3);
  String oper=s1.substring(1,2);
  int[] A1=getArray(a1);
  int[] A2=getArray(a2);
  type=operateCollection(A1,A2,oper);
  String str_new=strReplace(exp,s1,"T");
  System.out.println("->"+exp);
  System.out.println("->"+str_new);
  return operate(str_new);
  }
  }
  public static String strReplace(String rStr,String rFix,String rRep) {
  
  int l=0;
  
  String gRtnStr = rStr;
  
  do {
  l = rStr.indexOf(rFix,l);
  
  if(l == -1) break;
  gRtnStr = rStr.substring(0,l)+rRep+rStr.substring(l+rFix.length());
  
  l+=rRep.length();
  rStr=gRtnStr;
  }while(true);
  return gRtnStr.substring(0,gRtnStr.length());
  }
  public static int[] operateCollection(int[] A1,int[] A2,String ope){
  Mylist conn = new Mylist();
  if(ope.equals("+")){
  for(int num:A1){
  conn.add(num);
  }
  for(int num:A2){
  if(!conn.find(num)){
  conn.add(num);
  }
  }
  return getType(conn);
  }
  if(ope.equals("*")){
  for(int num_a:A1)
  for(int num_b:A2)
  if(num_a==num_b){
  if(!conn.find(num_a))
  conn.add(num_a);
  }
  return getType(conn);
  }

  if(ope.equals("-")){
      for(int num:A1){
         conn.add(num);
      }
      for(int num:A2){
          if(conn.find(num)){
              conn.remove(conn.findByvalue(num));
          }else{
              conn.add(num);
          }
      }
      return getType(conn);
  }
  else return null;
  

  }

  public static int[] getType(Mylist list){
  type=new int[list.size()];
  for(int i=0;i<list.size();i++){
  type[i]=list.get(i);
  }
  return type;
  }
  public static int[] getArray(String name){
  if(name.equals("A")||name.equals("a")){
  return A;
  }
  if(name.equals("B")||name.equals("b")){
  return B;
  }
  if(name.equals("C")||name.equals("c")){
  return C;
  }
  if(name.equals("T")||name.equals("t")){
  return type;
  }
  return null;
  }

  public static void initArray(){
  try{
  BufferedReader br = new BufferedReader(
  new FileReader("d:\input.txt"));
  String line="";
  int i=0;
  while((line=br.readLine()) !=null){
  i++;
  parse(line,i);
  }
  } catch(FileNotFoundException e){
  e.printStackTrace();
  } catch (IOException e) {
  e.printStackTrace();
  }
  }
  public static int[] parse(String line,int i){
  System.out.println(" "+line);
  String str=line.replace(" ", "").replace("{", "").replace("}", "");
  String[] num=(str.substring(2,str.length())).split(",");
  if(i==1){
  A = new int[num.length];
  for(int ni=0; ni<num.length;ni++){
  A[ni]=Integer.parseInt(num[ni]);
  }
  return A;
  }
  if(i==2){
  B = new int[num.length];
  for(int ni=0; ni<num.length;ni++){
  B[ni]=Integer.parseInt(num[ni]);
  }
  return B;
  }
  if(i==3){
  C = new int[num.length];
  for(int ni=0; ni<num.length;ni++){
  C[ni]=Integer.parseInt(num[ni]);
  }
  return C;
  }
  return null;
  }
  }

package math;

public class Mylist {
private int[] data=new int[3];
private int index=0;
private void expand(){
int[] data2=new int[data.length*2];
System.arraycopy(data,0,data2,0,data.length);
data=data2;
}
public void add(int o){
if (data.length==index) expand();
data[index]=o;
index++;
}
public void add(int pos,int o){
if (data.length==index) expand();
for(int i=index;i>pos;i--){
data[i]=data[i-1];
}
data[pos]=o;
index++;
}
public int remove(int pos){
int o=data[pos];
index--;
for(int i=pos;i<index;i++){
data[i]=data[i+1];
}
return o;
}
public int size(){
return index;
}
public int get(int pos){
return data[pos];
}

public boolean find(int i){
    for(int num:data){
        if(num==i) return true;
    }
    return false; 
}

public int findByvalue(int i){
    for(int i1=0;i1<data.length;i1++){
        if(data[i1]==i) 
            return i1;
    }
    return -1; 
}

public void clear(){
    index=0;
}
public boolean isEmpty(){
    return index==0;
}
public int[] toArray(){
    return data;
}

}

找个开源组件来实现

[code="java"]
import java.util.*;

// ...

Set a = new HashSet();
Set b = new HashSet();
Set c = new HashSet();
// use properties and String to read input file and initilized all sets
// assume you did that

Set result = new HashSet();
result.addAll(a); // make a copy of a, now result = a
result.addAll(b); // result = result + b

result.retainAll(c); // result = result * c

result.removeAll(b); // result = result - b

result.retainAll(a); // result = result * a
[/code]

input.txt
A = {5, 9, 10, 13, 56 }
B = {15, 8, 20 }
C = {78, 19, 10, 65 }